How do I restrict scaling to a specific axis?
Yes there is a way to do it.

During the scale S :


Use either X or Y or Z to scale only along X, Y or Z
Use either Shift+X or Shift+Y or Shift+Z to respectively scale (Y and Z but not X), (X and Z but not Y) or (X and Y but not Z)


And after you have confirmed your scale, you still have the operator panel in the bottom left part of the view :